Thursday

February 26, 2015

February 26, 2015

Total # Posts: 53

**Organic CHEM**

I read on the textbook a sentence like this: "The melting and boiling points of alkanes increase as their molecular sizes increase. This is because as alkane molecules become bigger, the attractive forces between the alkane molecules become stronger." Please tell me ...
*October 21, 2009*

**CHEM**

I posted a question earlier, and i'm still abit confused. What is the reaction between potassium and aqueous sodium chloride? I was told that the products are KOH, H2, and KCl. But shouldn't the reaction be a displacement reaction? Since Potassium is more reactive than...
*October 21, 2009*

**CHEM**

Please help me, i don't know how to approach this question! All ammonium salts on heating with sodium hydroxide produce ammonia gas. From which ammonium salt can the greatest mass of ammonia be obtained? a)0.5 mol of (NH4)3PO4 b)0.5 mol of (NH4)2SO4 c)1 mol of NH4Cl d)1 ...
*October 20, 2009*

**CHEM**

Which reactants could be used safely to prepare potassium chloride? 1. aqueous potassium hydroxide and dilute hydrochloric acid 2. aqueous potassium sulphate and aqueous sodium chloride 3. potassium and aqueous sodium chloride The answer is 1, but i don't really know how ...
*October 20, 2009*

**Biology**

Which trophic level gets the least amount of energy? a) producers b) herbivores c) carnivores d) decomposers I think the answer is c, but i'm not sure if it's right. I posted this question earlier, but google didn't provide with an answer. I still think the answer ...
*October 20, 2009*

**Chemistry**

Please check my workings to see if i'm correct, thanks! Find the percentage of nitrogen by mass in Ammonium nitrate, NH4NO3. (28/80)x 100% = 35% Is my answer correct?
*October 20, 2009*

**Biology!**

1. Urea is made where? Is it in the kidneys or the liver? 2. Which trophic level gets the least amount of energy? a) producers b) herbivores c) carnivores d) decomposers I think the answer is c, but i'm not sure if it's right.
*October 19, 2009*

**Urgent Chemistry question!**

How do i combine 2 half ionic equations into an overall equation?? 4OHˉ → 2H2O + O2 + 4e 2H+ + 2e → H2 *The "H+" is the hydrogen ion The correct overall equation is 2H2O → 2H2 + O2 How do i get that???
*October 19, 2009*

**Chemistry **

Does Sodium and potassium react with steam? Or is the reaction too violent to speak of?
*October 19, 2009*

**Math **

You mean "v" is an unknown? You cant solve an unknown without an equation.
*October 18, 2009*

**biology!**

A person has the blood group AB, what determines this blood group? a) different alleles on different chromosomes b) different alleles on the same chromosomes c) the same alleles on different chromosomes d) the same allele on the same chromosomes I thought that the answer ...
*October 16, 2009*

**Biology**

A variety of snail has an inherited condition that affects the thickness of the shell. The alleles are t and n. tt have thick shells tn have thin shells nn do not survive Two heterozygous snails are mated. What is the probability that a surviving snail of the next generation ...
*October 14, 2009*

**biology!**

What is the percentage of oxygen in expired air when a person is resting?
*October 14, 2009*

**Biology**

Which is the most direct way that the carbon in starch stored in cereal grain can be released to the atmosphere as carbon dioxide? 1. grain destroyed by fire 2. grain eaten by birds 3. grain made into bread and eaten by humans 4. grain stored in damp conditions goes mouldy and...
*October 12, 2009*

**Biology!!!!**

Which blood vessel contains blood that has high oxygen concentration, low carbon dioxide concentration, and high pressure? 1. aorta 2. pulmonary artery 3. pulmonary vein 4. vena cava I wrote the answer as 3, but is wrong. Which one is the correct answer?
*October 12, 2009*

**Biology!!!**

Which method of birth control prevents the implantation of the fertilised egg? 1. coil (mechanical) 2. condom (mechanical) 3. spermicide (chemical) 4. vasectomy (surgical) I don't get the question. The correct answer was number 1, but shouldn't all the options be ...
*October 12, 2009*

**Biology!!**

sorry! There's a mistake. the four choices are: 1. nucleus 2. cell wall 3. chloroplast 4. vacuole So which one is the correct option?
*October 12, 2009*

**Biology!!**

If i do a starch test on a plant cell that comes from a plant exposed to sunlight, which parts of the plant cell will be stained blueblack? 1. nucleus 2. cell wall 3. cytoplasm 4. vacuole I wrote the answer as 4, the vacuole, but the correct answer says 3, the cytoplasm. ...
*October 12, 2009*

**Biology!**

Inorganic fertiliser is applied each year to fields bordering a lake. the fertiliser runs off into the lake and causes six changes which altogether make the fish die. 1. aerobic bacteria feed on dead plants 2. algae reproduce faster 3. light cannot penetrate water 4. oxygen ...
*October 12, 2009*

**Biology!!!**

thanks
*October 12, 2009*

**Biology!!!**

The female mosquito is an effective vector for malaria. What makes it an effective vector? 1. it has wings 2. it lays many eggs 3. it makes noticeable noise 4. it mates several times I wrote the answer as B, but the answer as told on my assessment book says A, (which doesnt ...
*October 12, 2009*

**Biology!!**

I'd like to know, how many chromosomes are there for humans? (Correct me if i'm wrong) There are altogether 46 chromosomes, (or 23 pairs of chromosomes), which includes a pair of sex chromosomes.
*October 12, 2009*

**Biology!**

thanks
*October 12, 2009*

**Biology!**

What is the role of bacteria in the making of yoghurt from milk? 1. to make alcohol 2. to make carbon dioxide 3. to make lactic acid 4. to make lactose coagulate I think the answer is number 4, but i'm not so sure.
*October 12, 2009*

**science**

= 3 = When jellyfish reach adulthood they are about 95% water, so they are about the same density as water. That's why they float. Hope that's the answer you're looking for. :)
*October 10, 2009*

**chemistry **

sorry i submitted the question twice i think .
*October 10, 2009*

**chemistry **

In which reaction does the smallest percentage change in volume occur? a) C3H8 (g) + 5O2(g) ---> 3CO2(g) + 4H2O(l) b) 4NH3(g) + 3O2(g) ----> 2N2(g) + 6H2O(l) c) CH4(g)+ 2O2(g) ----> CO2(g) + 2H2O(l) d) 2H2S(g) + SO2 (g) ----> 3S(s) + 2H2O(l) The correct answer is A...
*October 10, 2009*

**chemistry **

In which reaction does the smallest percentage change in volume occur? a) C3H8 (g) + 5O2(g) ---> 3CO2(g) + 4H2O(l) b) 4NH3(g) + 3O2(g) ----> 2N2(g) + 6H2O(l) c) CH4(g)+ 2O2(g) ----> CO2(g) + 2H2O(l) d) 2H2S(g) + SO2 (g) ----> 3S(s) + 2H2O(l) The correct answer is A...
*October 10, 2009*

**chemistry**

elements x and y are from group 7 in the periodic table. x is a liquid at rtp, while y is a solid at rtp. which statements are correct? 1) atoms of y have more protons than atoms of x 2) molecules of y have more atoms than molecules of x 3) y displaces x from aqueous solutions...
*October 10, 2009*

**Chemistry **

A 0.1mol/dm^3 aqueous solution of phosphoric (V) acid, H3PO4, is mixed with a 0.1 mol/dm^3 of aqueous solution of sodium hydroxide. Which mixture will form the salt Na3PO4? a) 10cm^3 of H3PO4 with 30cm^3 of NaOH b) 10cm^3 of H3PO4 with 10cm^3 of NaOH c) 20cm^3 of H3PO4 with ...
*October 9, 2009*

**Literature: A Midsummer Night's Dream**

i'm studying A Midsummer Night's Dream, and i am a bit confused about the marriage of Theseus and Hippolyta. Please help! In act 1 scene 1, Theseus said "Hippolyta, i wooed thee with my sword and won thy love doing thee injuries". The modern translation of ...
*October 1, 2009*

**Quadratic**

This is the question: "Find the values of b and c for which x^2+bx+c is a factor of 2x^3-3x^2-3x-5." I was suggested to use long division, but how do i do long division when i don't know what b and c are??
*September 27, 2009*

**Trigonometry**

Given that a^2+b^2=2 and that (a/b)= tan(45degee+x), find a and b in terms of sinx and cosx. I don't know what i'm supposed to do, and i dont come to an answer! Help, thanks! my workings: tan(45+x)= (1+tanx)/(1-tanx) a/b = (1+tanx)/(1-tanx) a(1-tanx)=b(1+tanx) i square...
*September 27, 2009*

**Help!**

alright, i found the answer already.
*September 27, 2009*

**Help!**

Question: Given that (2^3x) x (7^2x) = 7^(x-1) x 2^(2x+2), find 14^x without using a calculator.
*September 27, 2009*

**Maths! **

Given that (2^3x) x (7^2x) = 7^(x-1) x 2^(2x+2), find 14^x without using a calculator.
*September 26, 2009*

**algebra 1**

I answered your previous question, and i think you should understand... but, anyways, you should know that all straight lines have the general equation y=mx+c. M being the slope/gradient, and c being the point at which the line cuts the y axis, also known as the y-intercept. ...
*September 26, 2009*

**Gradient of circle?**

I see! Thanks!
*September 26, 2009*

**Gradient of circle?**

A circle has the equation x^2+y^2-4x+6y-12=0 and i have already found that the centre has a coordinate of (2,-3), and a radius of 5 units. But i need to find points on the circle that has the gradient of -4/3 when a tangent is drawn on the point. How do i do that???
*September 26, 2009*

**algebra**

ok, the general equation of a line is y=mx+c, with m being the gradient, and the c being the y-intercept. so you already know that the line would be y=-4x+c. They told you a point on the line, so you subt that in. With x being -6, and y being 7. So, you should get 7=(-4)(-6)+c...
*September 26, 2009*

**?? Maths??**

Find the values of b and c for which x^2+bx+c is a factor of 2x^3-3x^2-3x-5 Ok, i've tried to find a factor of the quadratic function using trial and error. Let f(x) = 2x^3-3x^2-3x-5 f(1) is not equals to 0 f(-1) is not equals to 0 ... and i cant find a number that would ...
*September 26, 2009*

**Pre calculus**

You factorize the quadratic funtion on the left. x²-7x+10>0 (x-2)(x-5)>0 So the answer should be: x<2 OR x>5
*September 26, 2009*

**Integration**

Sorry i know how to do this already.
*September 26, 2009*

**Integration**

How should i integrate (4cos^2 - 1)? Do I use a certain formula??
*September 26, 2009*

**Trigo**

Given that a^2+b^2=2 and that (a/b)= tan(45degee+x), find a and b in terms of sinx and cosx. I don't know what i'm supposed to do, and i dont come to an answer! Help, thanks! my workings: tan(45+x)= (1+tanx)/(1-tanx) a/b = (1+tanx)/(1-tanx) a(1-tanx)=b(1+tanx) i square...
*September 26, 2009*

**Math**

Dont use a calculator. Just multiply the numerators together and the denominators together. You should get -234/64800
*September 26, 2009*

**math**

You mean factorize? bring out 5 from both sides. It's the highest common factor of both sides: 5(9c+5d)
*September 26, 2009*

**Math (Algebra)**

correct.
*September 26, 2009*

**bio**

yes, 3
*September 25, 2009*

**math**

1) (x+5)(3x-3) 2) 3x(x-1)
*September 25, 2009*

**Math**

what's your question?
*September 25, 2009*

**Scale**

The size of a country on a map with scale of 1:50000 is reflected as 2730.8cm^2, and the coastline is reflected as 386cm. The size of the country when drawn on another map with different scale, is 10923.2cm^2. Find the length of coastline reflected on the second map. I don'...
*September 24, 2009*

**Mathematics**

Help! I've tried this question and i don't come to a correct answer! The value of a property depreciated by 3.25% between 1997 to 2004, and appreciated by 2.75% between 2005 to 2008. In 1997, the value of the property was $75000, find its value in 2008. My workings: (...
*September 24, 2009*

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